quickest I have seen is about 40 minutes if there is no offload/onload of cargo.
True. But the fleet size of 787 is a lot smaller and the number of engine cycles they do will be a lot less compared to a 12 sector a day A320/B737 LoCo.
I don't know if anyone does 12 sectors a day consistently. I would guess 8 or 9 would be more realistic number. And yes, vs. a mature engine such as CFM56, which has been around 25+ years, it is a higher number of shutdowns, but still not a trend (2 different engines) vs. another medium-long haul aircraft such as A330 (2 engine shutdowns in same time frame as the 787 in the initial posting).